1 | ;
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2 | /** @module buffer */
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3 |
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4 | /**
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5 | * Make an invisible {@link canvas}.
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6 | * @param {number} width The width of the canvas
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7 | * @param {number} height The height of the canvas
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8 | * @returns {external:canvas} A canvas DOM element
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9 | * @private
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10 | */
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11 | function makeCanvas(width, height) {
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12 | var c = document.createElement("canvas");
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13 | c.width = width;
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14 | c.height = height;
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15 | return c;
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16 | }
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17 |
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18 | /**
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19 | * Make an invisible canvas buffer, and draw on it.
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20 | * @param {number} width The width of the buffer
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21 | * @param {number} height The height of the buffer
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22 | * @param {drawCallback} drawFun The callback that draws on the buffer
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23 | * @returns {external:canvas} The drawn buffer
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24 | */
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25 | function makeBuffer(width, height, drawFun) {
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26 | var canvas = makeCanvas(width, height);
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27 | var ctx = canvas.getContext("2d");
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28 | drawFun(ctx);
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29 | return canvas;
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30 | }
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31 |
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32 | /**
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33 | * Make a horizonally-flipped copy of a buffer or image.
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34 | * @param {external:canvas|external:image} buffer The original image
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35 | * @return {external:canvas} The flipped buffer
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36 | */
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37 | function flipBufferHorizontally(buffer) {
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38 | return makeBuffer(buffer.width, buffer.height, function(context) {
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39 | context.scale(-1, 1);
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40 | context.drawImage(buffer, -buffer.width, 0);
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41 | });
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42 | }
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43 |
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44 | /**
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45 | * Make a vertically-flipped copy of a buffer or image.
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46 | * @param {external:canvas|external:image} buffer The original image
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47 | * @return {external:canvas} The flipped buffer
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48 | */
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49 | function flipBufferVertically(buffer) {
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50 | return makeBuffer(buffer.width, buffer.height, function(context) {
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51 | context.scale(1, -1);
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52 | context.drawImage(buffer, 0, -buffer.height);
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53 | });
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54 | }
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55 |
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56 | module.exports = {
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57 | makeBuffer: makeBuffer,
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58 | flipBufferHorizontally: flipBufferHorizontally,
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59 | flipBufferVertically: flipBufferVertically
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60 | };
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